Electrical measurements in bipolar trickle reactors

Current potential curves for the total current flowing through the reactor and for the current passing through a single ring of the column packing have been measured using solutions containing the ferroferricyanide couple. The theoretical formulation of current-potential plots has been extended to incorporate a fast reversible reaction in the presence of diffusion polarization. A method for deriving the film thickness and mass transfer limiting current from these plots has been provided.List of symbols a integration constant in Equation 6 - b integration constant in Equation 8 - E applied potential (V) - E_r potential of the ring electrode with respect to the feeder electrode at the entry position of the reactor (V) - E₁,E₂ reversible potentials of an anodic and cathodic reaction, respectively - F Faraday constant - h film thickness (cm) - I current passing through segmented rings (mA) - I_F Faradaic current per unit length of wetted perimeter (A cm^–1) - I_NF non-Faradaic current per unit length of wetted perimeter (A cm^–1) - I_T total current per unit length of wetted perimeter (A cm^–1) - L half-length of Raschig ring (cm) - i_D limiting mass-transfer controlled current (A cm^–1) - i_D limiting mass transfer controlled current at the end of the rings (A cm^–2) - i_{D, 1mM} limiting mass transfer controlled current for 1 mM of redox couple - i_o1, i_o2 exchange current for two reactions (one anodic and the other cathodic) - n number of electrons transferred in an electrochemical reaction - n₁,n₂ number of electrons transferred in two reactions (one anodic and the other cathodic) - n_c number of mmol of ferro-ferricyanide - n_r number of graphite Raschig rings in a single layer of a packed column - r reaction rate (mol cm^–2 s^–1) - R gas constant (8.314JK^–1mol^–1) - r_o,r_i radii of the outer and inner perimeter of the ring (cm) - (Re)_f film Reynolds number (dimensionless) - T temperature (K) - v volumetric liquid flow rate (cm³ min^–1) - x axial co-ordinate along Raschig ring (cm) - ₁, ₂ transfer coefficients for two reactions (one anodic and the other cathodic) (dimensionless) - fraction of the end areas of the rings which overlap (dimensionless) - electrode overpotential (V) - _T total overpotential for half of a bipolar ring (V) - v kinematic viscosity (cm² s^–1) - solution resistivity ( cm) - _s potential in the solution phase (V)